How to Drain a Foundation

Order the perforated pipe and gravel from a building supply outlet.

Foundation drains install below ground where the soil contacts the building’s foundation. The drains prevent water from building up in the soil and damaging the concrete, undermining the foundation's stability and seeping through the foundation walls. The most common type of drainage system consists of perforated PVC pipe covered with a layer of gravel. Consult your local building department beforehand to determine the proper location for the exit point of the pipe. In some cases, a licensed contractor is required to connect the final section of drain to a sewer line or sump.

Trenching

1

Clear a 24-inch-wide area at all sides of the building's foundation. Remove any landscaped plants, bushes and sod from the area. Plants and bushes can be stored in pots. Sod is cut into strips and rolled up.

2

Dig a 24-inch-wide trench at all sides of the house's foundation with a shovel and digging bar. The trench is as deep as the foundation's footing, or lower edge of the foundation. Use the digging bar to carefully loosen dirt around natural-gas, water and sprinkler lines and remove that dirt from the trench.

3

Extend one end of the trench to the predetermined point where a contractor makes the connection to a sewer line or sump.

4

Measure the total linear footage of the trench, as well as the number of 90-degree corners of the foundation. Order 4-inch perforated PVC drainpipes and 90-degree elbows based on the calculations. Divide the linear footage of the trench by 27 to determine the cubic yards of gravel needed for a 12-inch layer over the pipes.

Pipes, Elbows and Gravel

1

Place full lengths of the perforated pipe end to end in the trench at all sides of the foundation. Fit the lengths of pipe together by inserting the uniform end of one into the flared end of another by hand. Cut the assembled sections of pipe at the midpoint of each corner of the trenches with a hacksaw.

2

Connect the sections of pipes at the corners of the trenches with 4-inch PVC elbows. Fit the elbows onto the ends of the pipes by hand. It's not necessary to glue drainpipe fittings when the pipes are underground.

3

Install a 12-inch-thick layer of gravel over the drainpipe at all sides of the foundation. Leave a 4-foot section of the pipe uncovered where the contractor makes the final connection to the sewer or sump.

4

Fill the trench with the soil that was removed when digging. Wet the soil lightly with a garden hose and allow the soil to dry and compact naturally. Wet the soil again and allow it to dry and compact a second time. Replant any sod, plants and bushes, as desired, after the final connection has been completed.

Things You Will Need

Shovel

Digging bar

Measuring tape

4-inch perforated PVC drainpipe

Hacksaw

4-inch PVC elbows

Gravel

Tip

For basement foundation walls, install an additional drainpipe at the level of the concrete footing.

About the Author

William Machin began work in construction at the age of 15, while still in high school. In 35 years, he's gained expertise in all phases of residential construction, retrofit and remodeling. His hobbies include horses, motorcycles, road racing and sport fishing. He studied architecture at Taft Junior College.